"Aesthetically, GEDmatch.com resembles an internal company wiki in need of an update. But what it offers to researchers and criminal investigators is tremendous flexibility. There are now more than 17 million DNA profiles in genealogical databases, but most of the bigger sites restrict what can be uploaded, banning not only crime scene evidence but anything processed by an external lab. GEDmatch will take it all — blood processed by an obscure lab, spit processed by 23andMe — for free, so long as it’s in the right format.How an Unlikely Family History Website Transformed Cold Case Investigations -- NYT
The site is also useful for people building an extensive family history. The average person can find any number of cousins on existing genealogy sites. But the key, for a genetic sleuth, is figuring out precisely how those cousins are related to a person of interest, and to each other. The tools that Mr. Olson created — primarily because he found the math intriguing — enable users to see the precise genetic segments where cousins overlap. From the site’s one million or so profiles, a skilled genetic detective can often puzzle out an individual’s identity from a single third cousin match.
“There’s nothing else like it,” said Barbara Rae-Venter, a genetic genealogist who used the site to help crack the Golden State Killer case."